Today, many electronic devices include memory systems to store information. Some memory systems store, for example, digitized audio or video information for playback by a respective media player. Other memory systems store, for example, software and related information to carry out different types of processing functions. Also, some types of memory systems such as, for example, Dynamic Random Access Memory (DRAM) systems and Static Random Access Memory (SRAM) systems are volatile memory systems in that stored data is not preserved when the power is off, whereas other types of memory systems such as, for example, NAND flash memory systems and NOR flash memory systems are nonvolatile memory systems in that stored data is preserved when the power is off.
As time progresses, consumers have an expectation that memory systems will have increasingly larger capacities provided by chips of increasing smaller size. Historically an important factor in the ability to do this has been the scaling down of process technology; however it is quite possible that in the near future the costs and limits of this approach could become increasingly more ominous. For example, as process technology is scaled down below 50 nm, it becomes extremely challenging to develop memory devices in smaller geometry, especially flash memories due to worsening transistor characteristics and reliability such as retention and endurance. Also, the scaling down of process technology is a huge investment. Thus, in view of the above costs and limits of the scaling down of process technology, there is a need to research and develop new ways to realize memory systems of increasingly larger capacities.